Cryptic corals thriving in dynamic environments may hold key insights into future coral reef habitats

Abstract

The coastal waters of Texas have dynamic environmental conditions and are heavily influenced by anthropogenic stressors, which are not conducive for corals. However, an unidentified coral has been documented for the first time in this ecosystem, specifically in Packery Channel, Texas, which is an artificial channel on jetty rocks connecting the Gulf of Mexico and Corpus Christi Bay. This research explored the strategies that these corals utilize to survive in rapidly fluctuating environmental conditions. Extensive in-water-field surveys were conducted in Packery Channel, Texas, over a year to 1) document environmental variability and 2) investigate the symbiotic relationship in the observed corals by a) measuring chlorophyll concentrations and symbiont densities and b) measuring the size of the corallites on each coral colony and zooplankton abundance within the jetty. Physical environmental data (e.g., turbidity, water temperature, and irradiance) and coral biological samples were collected within each season (e.g., winter, spring, summer, and fall). Additionally, plankton abundance measurements were assessed each season at the highest and lowest tides of the full-moon cycle. This study showed that these corals could withstand suboptimal environmental conditions, including broad water temperature (9.4–31.5 °C) and turbidity (2.5–95.3 NTU) ranges. Biological analyses show the most chlorophyll present per symbiont in the winter, while the spring, summer, and fall had the highest symbionts. This correlates with the environmental data fluctuating the least in the summer and fall (e.g., lower turbidity and higher irradiance measurements). This could suggest that the zooxanthellae cells were able to spend their energy on photosynthesis and reproduction in the fall and summer seasons rather than spending their energy to survive in the fluctuating environmental conditions in the winter season. Understanding how corals survive in rapidly fluctuating environmental conditions could provide insights into potential phenotypic plasticity.